Real-time image generation system for simulating physical paint, drawing media, and feature modeling with 3-D graphics

Abstract

A computer graphics painting system defined in terms of three dimensional graphics and texturing mapping. A three dimensional drawing primitive, most commonly a polygonal mesh, is directed along a path specified by a tablet, mouse, or other input stream. The primitive is transformed to sequential locations along the stroke in three dimensional space. At each location the primitive is processed with texture mapping techniques and blended into the frame buffer for real-time display. The brush primitive may take many forms to achieve a wide variety of painting effects and styles. The polygonal mesh form may also be active in conforming to any underlying surface or model data, thus enabling real-time painting of three dimensional objects.

What is claimed is: 
     
       1. In a computer system having memory and a movable pointing device, a brush for producing a brush stroke that paints a three dimensional object which is displayed in two dimensions on a graphics display device, said brush comprising, primitive data defined by a conforming polygonal mesh and stored in said memory for defining the size of said brush,   wherein said brush in response to the movement of said pointing device produces a paint stroke on said three dimensional object indicative of said primitive data.   
     
     
       2. A brush as recited in claim 1, further comprising, texture map data stored in said memory for representing a texture map corresponding to said polygonal mesh of said primitive data.   
     
     
       3. A brush as recited in claim 1, wherein said primitive data conforms to the surface geometry of said three dimensional object. 
     
     
       4. A system for painting a three dimensional object on a computer wherein a pointing device is moved to define a paint stroke and a graphics display unit exhibits the paint stroke, said system comprising: a central processor including means for receiving, from said moved pointing device, stroke signals defining said paint stroke as a series of locations on said three dimensional object, and means for providing primitive signals representative of a three-dimensional primitive at said series of locations and corresponding to a polygonal mesh;   a texture memory for storing texture data representative of a texture map of said three-dimensional primitive;   a graphics processor coupled to receive said primitive signals and including means for rendering said primitive signals at each of said series of locations according to said texture map to provide picture element signals representative of said paint stroke on said three dimensional object; and   a storage buffer including means for storing display data for driving said display unit, wherein said display data includes data representative of said picture element signals from said graphics processor blended with data representative of previous paint strokes.   
     
     
       5. A system according to claim 4 wherein said texture map includes transparency information. 
     
     
       6. A system according to claim 5 wherein said pointing device further provides force signals representative of the force manually applied to said pointing device and wherein graphics processor varies said picture element signals in accordance with both said force signals and said texture map. 
     
     
       7. A process for painting a three dimensional object on a computer wherein a painting device is moved to define a paint stroke and a display unit exhibits the paint stroke in real-time, the process including the steps of: defining said paint stroke as a series of locations traversed by said pointing device on said display unit;   providing primitive signals representative of a three dimensional primitive at said series of locations and corresponding to a polygonal mesh;   storing texture data representative of a texture map of said three dimensional primitive;   rendering said primitive signals at each of said series of locations according to said texture map to provide picture element signals representative of said paint stroke; and   storing display data for driving said display unit, wherein said display data is representative of said picture element signals blended with data representative of previous paint strokes.